It has been reported that unilateral resistance exercise will elicit strength gains in the unexercised contralateral limb at about 50% of the gains measured in the exercised limb. This study tested the hypothesis that a spillover effect may be present in proprioceptive neuromuscular facilitation (PNF) stretching techniques allowing for contralateral gains in range of motion from unilateral PNF stretching. Ss (M = 21; F = 15) attended a familiarization and maximal voluntary isometric contraction testing session and two counterbalanced experimental sessions. One experimental session consisted of the application of post-isometric relaxation PNF: straight leg raise to first point of bind, build from 30 to 70% of maximal voluntary isometric contraction over five seconds, hold 70% maximal voluntary isometric contraction for a further seven seconds, draw to new point of bind, hold for 12 seconds; and then repeat the cycle two more times. Isometric contractions were resisted by an anchored strap with a strain gauge in-line for real-time % maximal voluntary isometric contraction feedback. The second experimental session consisted of three unresisted straight leg raises to the point of bind 24 seconds apart. Range of motion of both limbs were measured using a liquid goniometer pre-intervention and after each of the three experimental cycles. EMG was measured in the homologous muscle of the contralateral limb to measure level of concurrent activation.

Three Ss were excluded from analysis: one due to injury and two due to EMG signals in excess of two standard deviations above baseline (indicating concurrent contraction). No significant changes were found in the range of motion of either limb for the unresisted straight leg raise session. The limbs that underwent the post-isometric relaxation PNF protocol showed significant increases in range of motion. A lesser, but still significant, increase in range of motion was also seen in the ‘dormant’ contralateral limb.

Implication. When PNF stretching is used after isometric contractions in a limb, the range of motion in the unstretched contralateral limb increases indicating that some degree of neurological crossover occurs. This finding has implications for injured limbs and their rehabilitation even when they are deliberately immobilized. Partial maintenance of pre-injury range of motion could be retained.